Not quite the same, but I have 2 classic 'race' bikes (that I've restored) they both require bump starting - and have now been converted to road bikes

My '75 250 Yamaha stroker I can push start easily - when cold select 2nd gear, walk alongside, drop clutch and grab clutch when she fires. Once warm, I can paddle start it

The Honda 350 K4 is another matter, high compression requires much more weight on the back wheel, so a slope or roller starters from cold is the easiest
When warm it will sometimes paddle start, but at the age of 68 I'm reluctant to run and bump by jumping on the saddle
So, I've developed a technique of getting her started. What I do is look for a pretty young lady with a strapping young man on her arm. I then ask him to give me a push, knowing that to impress his lady, there is no way he will stop pushing until it fires!
A couple of years ago, I described this method to an old couple a Laxey beach cafe. When it was time for me to leave, I executed my plan which worked perfectly and as I rode past them them, they were laughing and waving!

More on topic, I believe back in the day, that you were allowed a pusher provided you started at the back of the grid. I seem to recall Pat Mahoney doing it on his reluctant to start TZ700 for the first race when he won his third Lord of Lydden title 1975?